PROJECT ABSTRACT Current influenza vaccines are primarily delivered at peripheral sites and provide systemic serological immunity that is most commonly characterized by quantifying neutralizing antibody responses. We seek to complement this type of immunity with lung-initiated CD4 T cell immunity. Key features of the experimental design are vaccines that can exclusively elicit CD4 T cells and the option to incorporate linked innate activators. The premise that underlies the strategy described here is that CD4 T cells primed through the intranasal route will both establish resident memory cells within the lung and will foster development of memory cells that have rapid lung-homing potential. We hypothesize that these vaccine-primed lymphocytes can be mobilized rapidly upon natural infection and can directly provide long lasting and broadly protective immunity to future influenza virus infections. We will further hypothesize that these virus specific CD4 T cells will facilitate the recruitment and effector functions of other protective lymphoid cells. The goals of the work described here are thus to test these hypotheses and dissect the characteristics of elicited anti-viral CD4 T cells elicited by priming through the respiratory tract and evaluate the consequences for protection from influenza infection. These goals will be accomplished through completion of three Specific Aims, utilizing experimental tools previously established in our laboratory as well as novel strategies developed specifically for these experiments. Specific Aim 1. Design of viral antigenic ligand constructs for elicitation of influenza-specific CD4 T cells. Specific Aim 2. Assay the ability of lung vaccination with nano-lipoprotein-ligands to boost the abundance and functional potential of lung localized virus-specific CD4 T cells. Specific Aim 3. Determine whether intranasal vaccination potentiates recruitment and/or expansion of CD4 T cell and other effectors to the respiratory tract that protect from influenza virus infection.